Before Fort Meade's Tipton Airfield can be turned into the Baltimore region's newest civilian airport, the Army has a lot of blowing up to do.

Moving inch by inch, 41 munitions technicians are sweeping hand-held metal detectors across the airfield in what looks -- from a distance -- like a retiree beach outing.

But the technicians are probing for unexploded shells, mortars and grenades used during range training from 1917 to 1950.

"They were all, at one point, designed to kill people. They still can," says Richard Johnson, the project manager for Human Factors Applications, the private bomb-locater company hired for the $2.5 million cleanup.

Most of the squeals from the detectors lead technicians to ferrous rock or randomly discarded objects -- everything from horseshoes to jeep parts to a crab trap.

Occasionally -- about once every 425 beeps -- the technicians find an explosive. Ideally, they can dig it up and group it with other munitions for collective ignition. But most of the time the technicians leave the explosive in place, rig up the detonation cord and stand back -- way back.

Human Factors sets off the explosions four days a week in the middle of Fort Meade, even as commuters zip along nearby Route 32 and the Baltimore-Washington Parkway.

So far, the company has exploded more than 500 live munitions and is about halfway through the airfield. The Army then will give Tipton to Anne Arundel and Howard counties, which plan to operate it for small, noncommercial aircraft as soon as next spring.

Throughout the nation, the military has 1,878 active and 234 nonactive practice ranges, says Greg Mahall, a spokesman for the Army Environmental Center at Aberdeen Proving Ground.

Problems arise when the military turns over the ranges for civilian uses. In a well-known 1983 accident, two San Diego children were killed when they picked up an artillery shell on a former practice range at Camp Elliott. The range had been "surface-cleared" twice, according to the Army.

At Fort Meade, the 365-acre airfield is the last of nearly 10,000 acres to be converted to civilian use under the 1988 Federal Base Realignment and Closure Act.

The airfield is closed to everyone except the 41 technicians -- a 40-man, one-woman crew of military veterans, all of whom have graduated from the military's Explosive Ordnance Disposal (EOD) school at the Naval Surface Warfare Center in Charles County.

As civilians, they work on sites around the nation. "It's hard to get away from EOD, once you get into it," says Florida native Henry Kight, 25, describing his close bonds with his co-workers.

Their days at Fort Meade start at 6: 30 a.m. with a daily "safety briefing." The technicians gather in a parking lot to sip coffee, smoke cigarettes and listen to safety coordinator Mears. "Guys, pace yourself," Mears tells them one recent muggy morning. "We don't want to take any chances."

Smoking is not permitted in the working areas, where in May the company found 112 ordnance items -- including 23 projectiles, 10 rockets, 73 fuses, one mortar and five grenades.

One thing that makes finding explosives so difficult is having to ,, sift through many other items buried at Tipton.

The explosives are handled with far greater care. Historically, about 6 percent of all practice rounds have failed to explode at ranges throughout the nation, says Lenny Siegel of San Francisco State University, a national expert on the environmental aspects of closing military bases.

At Fort Meade, some of the shells have been waiting to explode since 1917, when the base trained 100,000 World War I "Doughboys." From that era, technicians are finding 6-pound and 1-pound cannon projectiles, says Ed Harris, supervisor of the bomb cleanup.

Unexploded shells continued to pile up during World War II training, when more than 3.5 million soldiers passed through Fort Meade, according to the Army. From that era, technicians are finding 75-mm cannon shrapnel projectiles, 2.36-inch bazooka rockets, MK2 "pineapple" grenades and M-9 rifle grenades.

Human Factors officials say their workers have never been injured by an explosion.

Human Factors -- a name that, one company official acknowledges, "doesn't sound like an outfit that ought to be blowing things up" -- is clearing explosives buried to depths of 4 feet.

Siegel acknowledged that 4 feet is deep compared to other Army cleanups.